Montana’s short summers require starting jicama indoors about eight weeks before the last expected frost date. Finding the best time to plant jicama in montana is tricky because this tropical root vegetable needs a long, warm growing season that our state just doesn’t naturally provide. But with careful timing and a few indoor tricks, you can still harvest a decent crop of these crunchy, apple-like tubers.
Jicama is a warm-weather plant that hates frost and needs at least 150 days of frost-free weather to mature. In most of Montana, our growing season is only 90 to 120 days. That means you have to start seeds indoors and use season-extending methods like row covers or a greenhouse. The key is knowing exactly when to start those seeds and when to move plants outside.
Understanding Montana’s Climate Zones
Montana spans USDA hardiness zones 3a through 5b, with some higher elevation areas dropping to zone 2. Your specific location matters a lot. Gardeners in the Bitterroot Valley or around Flathead Lake have slightly longer seasons than those in the high plains near Havre or Cut Bank.
Check your local frost dates. The average last spring frost ranges from early May in warmer valleys to early June in colder mountain areas. Your first fall frost can come as early as mid-September in some places. This narrow window is why timing is so critical.
Last Frost Date By Region
- Western valleys (Missoula, Kalispell): May 5-15
- South-central (Bozeman, Livingston): May 15-25
- Eastern plains (Billings, Miles City): May 10-20
- Northern high plains (Havre, Glasgow): May 20-30
- Mountain valleys (Butte, Helena): May 25-June 5
Best Time To Plant Jicama In Montana
For most Montana gardeners, the best time to plant jicama in montana is indoors about eight weeks before your last expected spring frost. If your last frost is May 15, start seeds around March 20. If it’s June 1, start around April 5. This gives the plants a solid head start before they face our short outdoor season.
You cannot direct sow jicama seeds in Montana ground. The soil never warms enough early enough. Even in late May, our soil temperatures often stay below 60°F, and jicama needs soil at least 65-70°F to germinate and grow well. Indoor starting is non-negotiable.
Step-By-Step Indoor Starting Schedule
- Count back 8 weeks from your average last frost date. Mark this on your calendar.
- Soak jicama seeds in warm water for 12-24 hours before planting to speed germination.
- Plant seeds 1/2 inch deep in 4-inch pots filled with seed-starting mix.
- Keep soil temperature at 75-85°F using a heat mat. Germination takes 10-14 days.
- Provide 14-16 hours of bright light once seedlings emerge. Use grow lights if needed.
- Harden off plants for 7-10 days before transplanting outdoors.
Transplanting Outdoors
Wait until nighttime temperatures stay above 50°F consistently. In Montana, this is usually 1-2 weeks after your last frost date. Soil should be at least 65°F. Use a soil thermometer to check. If your soil is cold, lay black plastic over the bed for two weeks before transplanting to warm it up.
Space plants 12-18 inches apart in rows 3 feet apart. Jicama is a vine that can spread 6-10 feet, so give it room. Install a trellis or fence for support. The vines will climb and produce more tubers when trained upward.
Season Extension Strategies For Montana
Even with perfect timing, Montana’s cool nights and early frosts can kill jicama before it matures. You need to protect your plants. Here are proven methods that work in our state.
Using Row Covers
Floating row covers add 5-10°F of frost protection and speed growth. Put them over plants right after transplanting and leave them on until daytime temperatures exceed 85°F. In late summer, replace covers to trap heat as nights cool down. This can extend your season by 2-4 weeks.
Greenhouse Or High Tunnel Growing
If you have a greenhouse or high tunnel, jicama grows much easier. You can start seeds 10 weeks before last frost and transplant into the protected space. The extra warmth and longer season make a big difference. Many Montana gardeners report good harvests this way.
Black Plastic Mulch
Lay black plastic over the soil before transplanting. It absorbs heat and warms the ground 5-10°F warmer than bare soil. Cut slits for the plants. This also suppresses weeds and conserves moisture. Use drip irrigation under the plastic for best results.
Soil Preparation And Fertilization
Jicama needs loose, well-draining soil rich in organic matter. Heavy clay soils common in parts of Montana will produce small, misshapen tubers. Prepare your bed by digging in 2-3 inches of compost or aged manure. Work the soil to at least 12 inches deep.
pH should be between 6.0 and 7.0. Test your soil and amend if needed. Add a balanced fertilizer like 10-10-10 at planting time. Avoid high-nitrogen fertilizers later in the season. Too much nitrogen makes lots of leaves but few tubers.
Watering Needs
Jicama needs consistent moisture, especially during tuber formation. Water deeply once or twice a week, providing 1-2 inches of water per week. Mulch with straw or grass clippings to retain moisture and keep soil cool. In Montana’s dry climate, drip irrigation works best.
Don’t let soil dry out completely. Stress from drought can cause cracked or woody tubers. But also avoid waterlogging, which rots roots. Good drainage is essential.
Growing Challenges In Montana
Montana presents unique challenges for jicama. The biggest is our short, cool season. Even with indoor starts and season extension, you might not get full-sized tubers. Expect smaller harvests than gardeners in warmer states. But the flavor is still great.
Pests And Diseases
Common Montana garden pests like aphids, flea beetles, and spider mites can attack jicama. Use insecticidal soap or neem oil for control. Row covers help prevent pest problems. Deer and rabbits may nibble leaves, so fencing might be needed.
Fungal diseases are less common in our dry climate, but powdery mildew can appear in late summer. Ensure good air circulation and avoid overhead watering. If mildew appears, treat with a baking soda solution.
Harvest Timing
Jicama is ready to harvest when the vines begin to yellow and die back, usually 150-180 days after planting. In Montana, this often happens just before the first fall frost. You must harvest before frost kills the vines, or the tubers will rot in the ground.
Dig carefully with a garden fork. Tubers can be 6-10 inches long and weigh 2-5 pounds in good conditions. Brush off soil but don’t wash them. Store in a cool, dark place like a root cellar at 50-60°F. They keep for several months.
Alternative: Growing In Containers
If your garden soil is too cold or heavy, grow jicama in large containers. Use 10-15 gallon pots with drainage holes. Fill with quality potting mix. Place containers in the sunniest spot, against a south-facing wall for extra heat. You can move them indoors if frost threatens.
Container-grown jicama needs more frequent watering. Check soil daily. Fertilize every 2-3 weeks with a balanced liquid fertilizer. The tubers might be smaller, but the control over temperature and moisture is worth it.
Indoor Growing Option
Some Montana gardeners grow jicama entirely indoors under grow lights. Use a 5-gallon bucket per plant. Provide 16 hours of light daily. Keep temperatures above 70°F. This works but takes up space and electricity. It’s more of a fun experiment than a practical food source.
Frequently Asked Questions
Can jicama survive a light frost?
No. Jicama is extremely frost-sensitive. Even a light frost of 32°F will kill the vines and damage tubers. Always harvest before the first frost. Use row covers or bring containers inside if frost is predicted.
How long does jicama take to grow in Montana?
Jicama needs 150-180 days from seed to harvest. With indoor starts and season extension, you can fit this into Montana’s growing season. But expect a longer wait than for tomatoes or peppers. Patience is key.
What if my jicama doesn’t form tubers?
This usually happens when nights are too cool or the season is too short. Jicama forms tubers in response to day length and temperature. In Montana, choose a short-season variety like ‘Mexican Yam Bean’ and use all the season extension tricks mentioned above.
Can I plant jicama seeds directly in Montana soil?
It’s not recommended. Our soil warms too slowly and the season is too short. Direct-sown seeds rarely produce tubers before frost. Always start seeds indoors 8 weeks before last frost for any chance of success.
What’s the best variety for Montana?
Look for ‘Early’ or ‘Short Season’ varieties. ‘Mexican Yam Bean’ is the most common. Some seed companies offer ‘Jicama de Agua’ which matures a bit faster. Avoid ‘Jicama de Leche’ which needs a longer season. Check with local nurseries for adapted strains.
Final Timing Summary
Here’s a quick timeline for Montana jicama growers. Adjust by 1-2 weeks based on your exact location and microclimate. Use this as a guide, not a strict rule.
- 8 weeks before last frost: Start seeds indoors
- 1-2 weeks after last frost: Transplant outdoors with protection
- Mid-summer: Apply row covers if nights cool below 50°F
- Early fall: Monitor for first frost, harvest before it hits
- After harvest: Store in cool, dark place for winter use
Growing jicama in Montana is a challenge, but it’s possible with careful planning. The best time to plant jicama in montana is early spring indoors, followed by a protected transplant in late spring. Don’t be discouraged if your first attempt yields small tubers. Each season you’ll learn more about your garden’s microclimate and how to push the limits. The crunchy, sweet reward is worth the effort. Try it this year and see what you can grow.